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How does an electric INDUCTION cooktop work?

January 8, 2019

 

 


 

In the past, there used to be only two mainstream options for stovetop burner selection:  Electric resistance and Gas flame. Now there’s a third option and it demands some attention since it is very energy efficient – electric induction cooktop.  In fact, if I were purchasing a cooktop today, I would choose induction.

 

These cooktops “look” very similar to a modern electric resistance cooktop with it’s glass top AND is also similar to these electric resistance cooktops since the energy input is all electricity (only a plug, no gas).  BUT the physics that is used to heat the food is quite different.

 

First, allow me to "geek out" for a moment.  We first have to establish a bit of baseline physics…DON'T STOP READING....this will be fairly easy and painless.  Give it a try...

 

An induction cooktop relies on two important connections between electricity and magnetism:

 

ELECTRICITY / MAGNETISM CONNECTION #1: Electric current creates (induces) a magnetic field.  Remember in elementary school when you took a nail, wrapped a wire around it, hooked it up to a battery and “PRESTO” the nail could now pick up paperclips…it became a MAGNET – this is what’s called an electromagnet.

 

Got that?  OK – so if electricity (the movement of electrons) creates a magnetic field, could the opposite also be correct?  Could a magnet create electricity (or the movement of electrons)?  Well yes….with an important clarification:

 

ELECTRICITY / MAGNETISM CONNECTION #2:   A changingmagnetic field (or a magnet in motion) causes the flow of electrons (electricity)!  Note that the magnetic field has to be CHANGING with time.  If you put a wire next to a magnet and leave it there…no electricity will flow in the wire.  BUT if you move the wire relative to the magnet, in other words, the wire “sees” a changing magnetic field …. electrons begin to move in the wire - you have induced electricity!

 

OK – so let’s apply this new cool physics understanding to induction cooktops…..

 

This induced electricity (moving electrons) can be in a metal wire  as described, OR they can be in another piece of metal…like a skillet or cooking pot!  

 

Presto – that’s an induction cooktop.  There is a large magnet (actually an electromagnet-see connection #1 above) under the glass cooktop…yep, a magnet, not a heating coil.  The electrons running through this electromagnet change direction (back and forth) rapidly and so the magnetic field around this electromagnet also changes rapidly, since the north pole of an electromagnet is dependent on the direction of the current.

 

Now – place the right kind of pan above this changing electromagnet and the electrons in the panwill “see” a changing magnetic field and will begin to move.  Since the pan has a high resistance to these moving electrons, their movement cause the PAN to heat and it can then cook the food!

 

Note that with a traditional electric resistance cooktop, electrons move through a high resistance burner, which gains temperature and then heats the pan, which then can heat the food.

 

With an induction cooktop, we skip the hot burner and the pan heats directly from the electromagnet. This makes it more energy efficient!

 

Pan materials

Since we have to get electrons moving in the pan, it is important that you choose the right kind of pan.  Not all pots and pans will work on an induction cooktop – they have to be magnetic. If a magnet sticks to the bottom of the pan, it will work on an induction cooktop.  Cast iron is ready to go and works perfect on induction.  Copper and aluminum pans … no luck, they will not work at all on an induction cooktop!  Many stainless steel pans that are all-clad have a layer built in which is magnetic so they will work – you just have to make sure to check before buying cookware.

 

The last advantage to induction cooktops is their response time.  Similar to a gas flame, once you turn the burner down on an induction cooktop, the electrons slow and the pan temperature drops rapidly – much quicker than it’s electric resistance counter part!

 

I hope this explanation helps you to explain induction cooktops.  Over time, the demand for these electric efficient stove tops has increased and I imagine that trend will continue.  Happy cooking!

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